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  • 1
    ISSN: 1432-1106
    Keywords: Cerebellum ; Rabbit ; Vestibul-oocular ; Optokinetic ; Adaptation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The vestibulo-ocular reflex (VOR) and optokinetic response (OKR) in the horizontal plane were examined in pigmented rabbits, using sinusoidal whole-body rotation and sinusoidal rotation of a striped screen. Sustained rotation of the animal (5° peak-to-peak, 0.1 Hz) for 4 h, under different optokinetic stimulus conditions, induced the following adaptive changes in the VOR: (1) outphase rotation of the screen (5°) increased the VOR gain by 0.3 (on average); (2) with the screen fixed in space, VOR gain increased by 0.2, (3) in-phase rotation of the screen (5°) decreased the VOR gain by 0.16. However, (4) in-phase rotation of the screen at twice (10°) the amplitude of whole-body rotation did not affect the gain. Instead, it induced a significant phase lead (23°) in the VOR, which did not occur in other stimulus conditions. Adaptive increases of the OKR gain occurred under sustained rotation of the screen alone (2.5°, 0.33 Hz). After bilateral destruction of floccular Purkinje cells with kainic acid the VOR gain and phase were affected only very slightly, but adaptive changes in the VOR were abolished. By contrast, the OKR gain was reduced and the OKR phase delayed. OKR adaptation was also affected in such a way that a gain increase initially produced could not be maintained during sustained screen rotation. Ablation of nodulus-uvala caused a gain increase and phase lead in both VOR and OKR, and its only effect on adaptability of the VOR or the OKR was observed for the VOR under stimulus condition (4).
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 80 (1990), S. 221-224 
    ISSN: 1432-1106
    Keywords: Vestibulo-ocular reflex ; Optokinetic eye movement response ; Flocculus ; Purkinje cell ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Single-unit activities were recorded from floccular Purkinje cells in 29 alert pigmented rabbits. The floccular areas specifically related to horizontal eye movement (H-zone) were identified by the effects of local stimulation and later confirmed histologically. Most of the 53 H-zone Purkinje cells responded to both vestibular stimulation with turntable oscillation (5° peak-to-peak, 0.1 Hz) in darkness and optokinetic stimulation with dot screen oscillation (2.5°, 0.33 Hz), often showing a preference either for turntable oscillation or screen oscillation. Since these responses were not correlated with the velocity of evoked eye movements or eye position shift, it is concluded that the major inputs to flocculus H-zone Purkinje cells are head velocity or retinal slip signals rather than eye velocity or position signals.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 77 (1989), S. 531-540 
    ISSN: 1432-1106
    Keywords: Vestibulo-ocular reflex (VOR) ; Adaptation ; Flocculus ; Purkinje cell ; Plasticity ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The responsiveness of floccular Purkinje cells to head oscillations was examined in alert pigmented rabbits subjected to adaptation of horizontal vestibulo-ocular reflex (HVOR) under three different combinations of turntable and screen oscillations. Purkinje cells involved in the HVOR control (H-zone cells) were identified by local stimulation effects that induced horizontal eye movements. In control states, simple spike discharages of H-zone cells were modulated predominantly out of phase with the velocity of sinusoidal turntable oscillation (0.1 Hz, 5° peak-to-peak). A sustained 180° outphase combination (5° turntable and 5° screen oscillation) was found to increase the average HVOR gain by 0.16, at which point the majority of H-zone cells increased the outphase simple spike modulation. A sustained inphase combination (5° turntable and 5° screen oscillation) decreased the average HVOR gain by 0.09, with the majority of H-zone cells decreasing the outphase simple spike modulation or becoming converted to the inphase modulation. With a vision-reversal combination (5° turntable and 10° screen oscillation), there was no change in the gain of the HVOR, but a moderate advancement in the phase. In this case, H-zone cells showed no appreciable changes in their simple spike modulation. Complex spike discharges of all H-zone cells tested were modulated in response to optokinetic stimuli involved in the combinations of turntable and screen oscillations. These results support the hypothesis that H-zone cells adaptively control HVOR dynamic characteristics through modification of mossy fiber responsiveness to head oscillation under influences of retinal error signals conveyed by climbing fiber afferents.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 77 (1989), S. 541-551 
    ISSN: 1432-1106
    Keywords: Adaptation ; Optokinetic response (OKR) ; Vestibuloocular reflex (VOR) ; Flocculus ; Purkinje cell ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Sustained sinusoidal oscillation of a striped cylindrical screen around a stationary, alert pigmented rabbit with certain parameters (for 4h, 5°, 7.5°, or 10° peak-to-peak, 0.1 or 0.2 Hz) adaptively modified not only the horizontal optokinetic response (HOKR) but also the horizontal vestibulo-ocular reflex (HVOR). The major effects thus obtained during 4 h were an increase in the HOKR gain by 0.23, and that of the HVOR gain by 0.18. Bilateral destruction of floccular Purkinje cells with microinjection of kainic acid abolished these effects on both HOKR and HVOR. Single unit activities of floccular Purkinje cells were recorded from the floccular areas related to horizontal eye movements (H-zone) with local stimulus effects. Most H-zone Purkinje cells normally exhibited modulation of simple spike discharge in phase with screen velocity and out of phase with turntable velocity. Sustained screen oscillation (7.5°, 0.1 Hz) for 1 h increased the simple spike responses not only to screen but also to turntable oscillation. No such changes were observed in other floccular areas. These observations suggest that sustained optokinetic stimulations induce adaptation of HVOR through an interaction of retinal slip and head velocity signals within the flocculus or its related neuronal tissues.
    Type of Medium: Electronic Resource
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